SAN ANTONIO  The first and only time Cody Ransom started an Opening Day, he was wearing spotless pinstripes.

Oh, and filling in for some Yankees third baseman named Alex Rodriguez. Rodriguez later returned from hip surgery and Ransom tore a quad after only 79 major-league at-bats that season, but the veteran infielder would come out of his New York stint with a World Series ring.

“Hopefully,” Ransom said with a smile Saturday morning, “we get the same result at the end of this season.”

Four years after subbing for A-Rod, the Padres newcomer has another unexpected assignment: replace All-Star Chase Headley at third base in Monday’s season opener against the New York Mets.

Originally projected to begin the season with Triple-A Tucson, Ransom made his third career Opening Day roster after Headley’s fractured thumb and Logan Forsythe’s plantar fasciitis opened a spot for the 37-year-old.

“You never wish injury on anybody,” said Ransom, who will be in the lineup Monday against left-hander Jonathon Niese. “Unfortunately, it’s part of the game.”

Ransom has bounced around in that game for the last 15 years, recording 5,007 minor-league at-bats but only 583 for six major-league teams. Nearly half of those came last year, when he played in a total of 90 games for Milwaukee and Arizona.

He hit .220 (.264 against lefties) with 11 home runs and 42 RBI — both career-highs.

“To be able to get at-bats last year was a lot of fun,” said Ransom, who signed a minor-league contract with the Padres in December. “I’m used to doing that in the minor leagues. It gives you a chance to not worry about going ‘ohfer’ one day, because you’re gonna get a chance to redeem yourself.

“There’s not as much pressure on you, not from the outside, but internal pressure, pressure you put on yourself. You’re able to relax a little more.”

Now, with Headley possibly out for the first month, Ransom figures to continue seeing regular playing time. He’s likely to start at third whenever a lefty takes the mound.

“I am who I am,” Ransom said. “All I can do is play the game I know how to play. I can’t try and be Chase. I couldn’t try and be Alex back then. I’ve been doing this for 16 years now. You’re gonna get what you’re gonna get.”

And when Headley and, later, Forsythe return? That’s when Ransom’s versatility could become especially convenient.

“Whatever they need. I’ve done a little bit of everything,” said Ransom, who will wear No. 1 this season. “If they want to move me around, I can play anywhere in the infield, play a couple games in the outfield.”

Ransom’s major-league experience spans 146 starts at shortstop, 80 at third, 34 at second, 24 at first and one in left field.

“Cody was projected to probably go to Tucson,” Padres manager Bud Black said, “and add depth and experience to our group down there and, in case there was a need, to come up and provide it.”

The need has arrived sooner than anyone, Ransom included, expected. Injuries aside, that’s not a bad thing for Black, who’s already comfortable with his new infielder.

“It’s tough coming into a new team, and all of a sudden you’re on the team,” Black said. “But I think he’s a guy that, as far as coming onto our group, knowing our bunt plays, our pick-off plays, knowing how to play our game — no worries. He knows how to play.”